1. Field of the Invention
The present invention relates to a metallic cylindrical member and a metallic bracket. Particularly, the invention is concerned with a metallic cylindrical member and a metallic bracket, which are formed by joining a pair of sides of a metallic plate.
2. Description of the Prior Art
According to the prior art, as shown in FIG. 37, a generally square pipe-shaped metallic frame 1a with an axis oriented in a nearly horizontal direction is disposed at an upper position in the interior of a seat back 1 of a first seat mounted on an automobile, and generally square pipe-shaped metallic brackets 1b and 1c having axes oriented nearly vertically are attached to the metallic frame 1a. 
Generally cylindrical headrest supports 3 and 4 are inserted into the metallic brackets 1b and 1c, the headrest supports 3 and 4 supporting headrest stays 2a and 2b which are projected substantially in a vertically downward direction from the headrest 2.
As shown in FIG. 38, the metallic brackets 1b and 1c are each formed in the shape of a square pipe by bending a metallic plate so that left and right sides of the metallic plate are opposed to each other and by subsequently joining the opposed sides. The portions to be joined of the metallic brackets 1b and 1c are designed to take spring-back into account and therefore a clearance of a predetermined width is formed between both sides of the metallic plate.
The joined portions are brought into a substantially closely contacted state with one flat wall surface of the metallic frame 1a and in this state welding is applied to between the bent portions of the metallic brackets 1b, 1c and the wall surface of the metallic frame 1a abutted against the bent portions, whereby the metallic brackets 1b and 1c are fixed to the metallic frame 1a. 
In the above conventional metallic cylindrical member, since the metallic brackets 1b and 1c are welded to the metallic frame 1a, welded portions 5 shown in FIG. 38 shrink on cooling. With this shrinkage of the welded portions 5, the bent portions of the metallic brackets 1b and 1c abutted against the metallic frame 1a are pulled away from each other. Consequently, the sides of the metallic brackets 1b and 1c move away from each other, resulting in a wider width than the foregoing predetermined width. Thus, there has been a problem that an inside diameter of the metallic cylindrical member is changed by welding despite the inside diameter being designed to a value which permits the headrest supports to be supported without clearance in a state before welding.
Accordingly, the present invention aims to solve said problems and to provide a metallic cylindrical member and a metallic bracket both able to suppress a change in inside diameter which is caused by an external force applied on cooling of a welded portion.
In one aspect, the invention is constructed such that concave and convex shapes adapted to engage each other in an anti-dislodgment manner are formed at a pair of sides of a metallic plate, then both sides are confronted with each other and the concave and convex shapes are put in engagement with each other to join both sides.
In this construction, when a pair of sides of a metallic plate are opposed to each other and concave and convex shapes formed at both sides are engaged with each other to join both sides, both sides are engaged with each other in an anti-dislodgment manner and are thereby joined strongly.
According to this construction, when the metallic cylindrical member thus formed is welded to another metallic member, even if the welded portion shrinks on cooling and an external force is applied in a direction in which are joined sides are pulled apart from each other or in a direction in which the joined sides are abutted against each other, displacement of both sides joined strongly is prevented and hence a change in inside diameter of the metallic cylindrical member is prevented.
Thus, it is possible to provide a metallic cylindrical member able to prevent a change in its inside diameter which is caused by an external force applied on cooling of the welded portion.
In another aspect, the invention is constructed such that the concave and convex shapes formed on both sides of the metallic plate may by formed so as to have approximately equal shortest distances in the seam direction.
More specifically, the concave and convex shapes are formed so that a shortest distance in the seam direction of a concave or convex shape formed on one side is approximately equal to a shortest distance in the seam direction of a concave or convex shape formed on the other side.
That is, when plural projections are formed on each side and opposed projections are engaged with each other, the sum of shortest distances in the seam direction of the projections formed on one side and the sum of shortest distances in the seam direction of the projections formed on the other side become almost equal to each other. This enables to enhance the strength of the joined portion.
Note that where such projections as mentioned above are formed, the xe2x80x9cshortest distancexe2x80x9d on each side indicates the sum of minimum widths of the projections in the seam direction. If the projections are constricted at their base portions, the shortest distance in question indicates the sum of widths of the base portions in the seam direction.
The concave and convex shapes may be formed so that the shortest distance throughout the whole of one side and the shortest distance throughout the whole of the other side are almost equal to each other. Alternatively, the concave and convex shapes may be formed so that the shortest distance in part of one side and the shortest distance in part of the other side are almost equal to each other.
In another aspect, the invention is constructed such that as an example of a method for joining both sides together, both sides may be crushed in the thickness direction at portions including mutually opposed concave and convex shapes in an engaged state of the concave and convex shapes formed on both sides.
According to this construction, when the concave and convex shapes formed on both sides are engaged with each other, both sides are crushed in the thickness direction at portions including mutually opposed concave and convex shapes and are joined together.
As a result, metal is shifted from the crushed portion toward the concave/convex boundary, whereby the adhesion at the boundary is enhanced and so is the strength of the joined portion.
In another aspect, the invention is constructed such that as an example of the crushing, both sides may be crushed stripewise into indentations at portions including the concave and convex shapes.
In this case, when stripe-shaped indentations are formed by crushing so as to include the concave and convex shapes, metal is dispersed from the indentations toward the concave/convex boundary. This enables to easily enhance the strength of the joined portion.
In another aspect, the invention is constructed such that as an example of forming such indentations, the indentations may be formed by crushing both sides stripewise at portions including the concave and convex portions while allowing the stripes to escape obliquely relative to the concave/convex boundary.
According to this construction wherein indentations are formed stripewise obliquely relative to the boundary, metal is dispersed widely in the seam direction. Thus, this method is useful for dispersing metal widely around the boundary and thereby realizing a strong joint of both sides.
Thus forming indentations while allowing escape obliquely relative to the concave/convex boundary is advantageous in that metal can be dispersed widely in the seam direction. But from the standpoint that it suffices for the indentations to be formed by crushing both sides stripewise at portions including the concave and convex shapes, they also may be formed in a direction nearly perpendicular to the concave-convex boundary. This permits the joining strength to be enhanced over a wide range in the seam direction.
A mere formation of indentations is useful in that the strength of the joined portion can be enhanced easily, but such a construction is merely one example.
In another aspect, the invention is constructed such that as an example of the crushing, both sides may be crushed generally circularly to form indentations (dents) at portions including the concave and convex shapes.
In this case, generally circular dents are formed by carrying out the crushing so as to include the concave and convex portions, whereby metal is dispersed from the indentations toward the concave/convex boundary. According to this construction, since metal is dispersed from a relatively wide area, that is, since much metal is fed to the boundary, it is possible to realize a stronger joining. This construction is useful in this point. This enables to feed a larger amount of metal to the concave/convex boundary and enhance the strength of the boundary.
In another aspect, the invention is constructed such that as an example of the crushing, both sides may be crushed bandwise to form indentations at portions including the concave and convex portions in such a manner as to provide a larger width on the side spaced apart from the concave/convex boundary.
According to this construction, band-like dents are formed by crushing both sides at portions including the concave and convex portions. As a result, metal is dispersed from the dents toward the convex/concave boundary. In this case, since the dents are formed so as to be wider on the side spaced apart from the boundary, metal can be dispersed to the boundary from portions spaced apart from the boundary. Consequently, it is possible to supply a sufficient amount of metal to the boundary while diminishing a thin-walled area adjacent to the boundary. In this point this construction is useful.
In another aspect, the invention is constructed such that as an example of the crushing, both sides are crushed bandwise to form indentations at portions including the concave and convex portions in such a manner that narrow and wide portions are formed alternately in directions away from the concave/convex boundary with the boundary portion formed wide.
According to this construction, when band-like dents are formed by crushing both sides at portions including the concave and convex portions, metal is dispersed from the dents toward the concave/convex boundary.
At this time, since the dents are wide at the boundary, the joining strength is enhanced over a wide area in the seam direction. Besides, since narrow and wide portions are alternate in directions away from the boundary, a larger amount of metal can be collected efficiently toward the boundary from the side away from the joined portion. This construction is useful in this point. This enables to feed a larger amount of metal to the concave/convex boundary from the portion spaced apart from the boundary while maintaining the strength of the portion adjacent to the boundary and thereby realize a strong joint.
In another aspect, the invention is constructed such that as a concrete application example of the metallic cylindrical member, plural projections adapted to engage each other in an anti-dislodgment manner are formed on a pair of sides of a metallic plate so that shortest distances in a seam direction of the projections on both sides are almost equal to each other. While allowing a joined portion to be included in one generally flat wall surface, both sides of the metallic plate are opposed to each other and the projections are brought into engagement with each other, followed by stripewise crushing at portions including the projections to form indentations, allowing both sides to be joined together, whereby the metallic plate is formed into a generally square pipe as a metallic cylindrical member. A generally pipe-like metallic frame is disposed with its axis oriented nearly horizontally at an upper position in the interior of a seat back of a first seat which is mounted on an automobile, and bent portions of the metallic cylindrical member abutted against a generally flat wall surface of the metallic frame are welded to the said wall surface in a state in which the axis of the metallic cylindrical member is oriented in a substantially vertical direction and in which the joined portion is in substantially close contact with the wall surface of the metallic frame. Further, a generally cylindrical headrest support which supports a headrest stay projected in a nearly vertically downward direction from the headrest is inserted into the metallic cylindrical member from above nearly vertically.
Thus, the present invention is useful also as a metallic bracket which supports a headrest support in a seat back of a first seat installed in an automobile.
In this way it is possible to provide a metallic bracket which supports a headrest support in a seat back of a first seat installed in an automobile and which can prevent a change in its inside diameter caused by an external force developed on cooling of the welded portions.
In another aspect, the invention is constructed such that as a concrete application example of the metallic cylindrical member, plural projections adapted to engage each other in an anti-dislodgment manner are formed on a pair of sides of a metallic plate so that shortest distances in a seam direction of the projections on both sides are almost equal to each other. While allowing a joined portion to be included in one generally flat wall surface, both sides of the metallic plate are opposed to each other and the projections are brought into engagement with each other, followed by stripewise crushing at portions including the projections to form indentations, allowing both sides to be joined together, whereby the metallic plate is formed into a generally square pipe as a metallic cylindrical member.
A pair of pipe-like metallic frames are disposed at upper positions in the interior of a seat back of a second or third seat mounted on an automobile, the metallic frames being disposed in nearly parallel with each other at a predetermined interval while allowing their axes to be oriented in a substantially horizontal direction, and bent portions of the metallic cylindrical member abutted against generally flat wall surfaces of the metallic frames are welded to the said wall surfaces in a state in which the metallic cylindrical member spans the metallic frames while allowing the axis of the metallic cylindrical member to be oriented in a substantially vertical direction and in which the joined portion is in substantially close contact with the wall surfaces of the metallic frames. Further, a generally cylindrical headrest support which supports a headrest stay projected in a nearly vertically downward direction from the headrest is inserted into the metallic cylindrical member from above nearly vertically.
Thus, the present invention is further effective as a metallic cylindrical member which supports a headrest support in a seat back of a second or third seat installed in an automobile.
According to this construction it is possible to provide a metallic bracket which supports a headrest in a seat back of a second or third seat installed in an automobile and which can prevent a change in inside diameter caused by an external force developed on cooling of the welded portions.
Other and further objects, features and advantages of the invention will appear more fully from the following description.